1. Field of the Invention
This invention relates to a preservative system, household and personal product compositions containing the preservative, and a method for inhibiting the growth of microorganisms.
2. The Prior Art
Many household and personal product formulations, including their raw material components, are susceptible to microbiological contamination. Such compositions include dishwashing detergents, laundry liquids, fabric softeners and liquid soaps among others. Preservatives are frequently added to these formulations to protect them against microbial spoilage. Contaminating microbes are, however, adaptable. Given time, they often become immune to the preservative. Therefore, there is a continuing need for new preservatives.
Foremost among the preservatives for household products has been formaldehyde. Treatment with this chemical is effective and economical. Unfortunately, there have been some studies implicating formaldehyde with mutagenicity. Prudence has dictated a search for alternatives. Glutaraldehyde can substitute as a preservative but it must be employed at reasonably high levels and is 20 times more expensive per pound. Kathon CG, a trademark of Rohm & Haas, representing a mixture of 4 chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one is effective in extremely low amounts. Yet, it costs 10 times as much as glutaraldehyde. Consequently, it is not as cost effective as traditional formaldehyde. Economical alternatives are needed.
Mixtures of 4-(2-nitrobutyl)morpholine (I) and 4,4'-(2-ethyl-2-nitrotrimethylene)dimorpholine (II) have been known for their anti-microbial properties in metalworking fluids and cooling waters for pulp and paper mills. Commercial literature prescribing the method of use for these mixtures recommends pH be controlled above 6.0. While the morpholine/dimorpholine mixtures have many desirable properties, they also suffer from several disadvantages. To obtain good anti-microbial activity, fairly high concentrations must be present. Patents and commercial literature suggest concentrations from 500 to 3000 ppm or higher are necessary to be effective. Cost and water-solubility are further problems.
Combinations of I and II with other anti-microbials have been described which overcome the problem of high concentration. In U.S. Pat. No. 4,101,433, a 3.5:1 mixture of I/II combined with tris(hydroxymethyl)nitromethane was disclosed to be active at 500 to 1500 ppm total concentration. Shema et al in a series of patents report increasing the effectiveness of 4-(2-nitrobutyl)morpholine by combination with either 2,4,5-trichlorophenol, 3,4',5-tribromosalicylanide, 2,2-dibromo-3-nitriloproprionamide, N-alkyl-dimethyl-benzyl ammonium chloride, a 2-methyl-4-isothiazolin-3-one calcium chloride mixture or hexachloro dimethyl sulfone; see U.S. Pat. Nos. 3,860,516, 3,862,034, 3,897,554, 3,881,008, 3,929,563 and 3,917,834, respectively. All these patents recognize the need to improve the efficacy of the generally desirable I and/or II compositions.
Accordingly, it is an object of this invention to provide an improved preservative containing I, II or mixtures thereof that is an effective anti-microbial agent at low concentrations.
Another object of this invention is to provide household and personal cleaning or conditioning compositions containing the preservative.
A further object of this invention is to provide a more efficient method for inhibiting the growth of micro-organisms.